Treating shale and clay in hydrocarbon producing formations

ABSTRACT

Clay is stabilized in the drilling of wells and other formation treatment for hydrocarbon production by the addition to the drilling or other fluid fluid of potassium formate together with a cationic formation control additive.

RELATED APPLICATION

This application is based upon Provisional Application Ser. No.60/192,304 filed Mar. 27, 2000, and claims the full benefit of itsdisclosure, claims and filing date.

TECHNICAL FIELD

This application relates to the drilling of wells in the production ofoil, gas and other fluids from underground formations, and particularlyto the stabilization of boreholes drilled for the production ofhydrocarbons. It includes the treatment of shale and clay in situ toprevent swelling caused by the absorption of water from drilling fluids.

BACKGROUND OF THE INVENTION

A good description of the problem which this invention addresses in thecontext of formation drilling may be found in an article by Thomas W.Beihoffer et al in the May 16, 1992 Oil & Gas Journal, page 47 et seq.,entitled “Cationic Polymer Drilling Fluid Can Sometimes ReplaceOil-based Mud.” As stated therein, “(S)hales can become unstable whenthey react with water in the drilling fluid. These reactive shalescontain clays that have been dehydrated over geologic time by overburdenpressure. When the formation is exposed, the clays osmotically imbibewater from the drilling fluid. This leads to swelling of the shale,induced stresses, loss of mechanical strength, and shale failure.” Shalecrumbling into the borehole (“sloughing”) can ultimately place a burdenon the drill bit which makes it impossible to retrieve.

Salts such as potassium chloride have been widely used in drillingtreatments to convert the formation material from the sodium form by ionexchange to, for example, the potassium form which is less vulnerable toswelling; also the use of high concentrations of potassium salts affectsthe osmotic balance and tends to inhibit the flow of water away from thehigh potassium salt concentrations into the shale. However, it isdifficult to maintain the required high concentrations of potassiumsalts in the drilling fluids. In addition, the physical introduction ofsuch salts causes difficulties with the preparation of the viscosifyingmaterials typically used for drilling. Inorganic salts can also have aharmful effect on the environment if released.

As background for the present disclosure, I have assembled prior artreferences representative of three general types of amine and quaternaryammonium cation sources which have been suggested for clay treatment inhydrocarbon recovery. These are (a) single-site quaternaries and amines,(b) compounds having a few (two to about six) amine or quaternaryammonium cation sites, which I have called “oligocationic”, and (c)quaternary ammonium or amine polymers, which may have from about six tothousands of cationic sites. The entire specifications of all of thepatents set forth below are incorporated by reference, as the cationicmaterials described therein are useful in my invention.

A. Single-Site Quaternaries and Amines: Brown U.S. Pat. No. 2,761,835,Brown U.S. Pat. No. 2,761,840, Brown U.S. Pat. No. 2,761,836, Himes etal U.S. Pat. No. 4,842,073, Thomas and Smith U.S. Pat. No. 5,211,239.

B. Oligocationics: Brown U.S. Pat. No. 2,761,843; Krieg U.S. Pat. No.3,349,032.

C. Polycationics: Borchardt et al U.S. Pat. No. 4,447,342, McLaughlin etal U.S. Pat. No. 4,374,739 McLaughlin et al U.S. Pat. No. 4,366,071.

SUMMARY OF THE INVENTION

My invention includes the use of combinations of potassium formate withvarious cationic materials, for the treatment of clay and shale insubterranean formations during drilling and otherwise for thestabilization of clay and clay-containing shale. For purposes of thispatent application, it should be noted that all of the above identifiedpatents incorporated by reference address problems similar to theproblem I address. Each of the patents employs cationic formationcontrol additives for drilling fluids to help control the swelling andsloughing of shale and clay contacted by aqueous drilling and otherformation treating fluids. The contexts of use of such additives and thetechniques for employing them as described in those patents are entirelyconsistent with and compatible with my invention. That is, I employ myown combination of additives in drilling fluids and otherwise to treatshale and clay to control swelling and sloughing.

Although the entire specifications of the above listed patents areincorporated by reference, to help in defining the materials useful inthe present invention, I refer specifically to parts of the aboveidentified patents, namely:

Brown U.S. Pat. No. 2,761,835 columns 3-10, Brown U.S. Pat. No.2,761,840 columns 5-6, Brown U.S. Pat. No. 2,761,836 columns 5-6, Himesand Vinson U.S. Pat. No. 4,842,073 columns 1-10, Thomas and Smith U.S.Pat. No. 5,211,239 columns 1-2, Brown U.S. Pat. No. 2,761,843 columns3-6, Krieg U.S. Pat. No. 3,349,032 columns 3-12, McLaughlin et al U.S.Pat. No. 4,366,071 columns 7-14, and Borchardt et al U.S. Pat. No.4,447,342 columns 17-20.

It will be seen from these passages and excerpts (the full disclosuresof the patents, as indicated above, are incorporated in theirentireties) that the three general types of cationic materials I may usein my invention for the stabilization of clay in subterranean formationsare single-site cationics, oligocationics, and polycationics. Togetherthey may be referred to herein as “cationic formation controladditives.” Although cationics derived from sulfur, phosphorous andother elements capable of forming water-soluble cationic sites areeffective and included in my invention, I prefer to use amine orammonium-based cations. Thus the cationic portion of my clay treatmentcomposition is preferably an amine or ammonium based (succinctly,“nitrogen-based”) cationic material. I may use any of the cationicmaterials described in the above identified patents.

The single site amine and quaternaries useful as cationic formationcontrol additives in my invention include di-, tri, and tetra- alkylsubstituted amine and ammonium compounds wherein the alkyl groupsinclude from 3 to 8 carbon atoms (Brown U.S. Pat. No. 2,761,835);substituted pyridine, pyridinium, morpholine and morphilinium compoundshaving from 1 to 6 carbon atoms in one or more substituent groups (BrownU.S. Pat. No. 2,761,840), additional heterocyclic nitrogen compoundssuch as histamine, imidazoles and substututed imidazoles, piperazines,piperidines, vinyl pyridines,and the like as described in Brown U.S.Pat. No. 2,761,836, the trialkylphenylammonium halides,dialkylmorpholinium halides and epihalohydrin derivatives described byHimes et al in the U.S. Pat. No. 4,842,073 patent, and the allylammonium compounds of the formula (CH₂═CHCH₂)_(n)N⁺ (CH₃)_(4-n) X⁻whereX⁻ is any anion which does not adversely react with the formation or thetreatment fluid, described by Thomas and Smith in U.S. Pat. No.5,211,239. Preferred single site quaternaries are diallyl dimethylammonium chloride (that is, the above formula where n═2 and X⁻is Cl⁻),and tetramethyl ammonium chloride, sometimes referred to as TMAC.

Oligocationics useful as cationic formation control additives in myinvention include di- and polyamines (up to 100 nitrogens) substitutedwith alkyl groups having up to 12 carbon atoms (one or more of thenitrogens may be quaternized) as described by Brown in U.S. Pat. No.2,761,843, and polyquaternaries described by Krieg in U.S. Pat. No.3,349,032, namely alkyl aryl, and alkaryl bis- and polyquaternarieswherein two quaternary ammonium nitrogens are connected by variousconnecting groups having from 2-10 carbon atoms.

Polyquaternary (cationic) formation control additives useful in myinvention include those described by McLaughlin in the U.S. Pat. No.4,366,071 and U.S. Pat. No. 4,374,739 patents, namely polymerscontaining repeating groups having pendant quaternary nitrogen atomswherein the quaternizing moieties are usually alkyl groups but which caninclude other groups capable of combining with the nitrogen andresulting in the quaternized state. I may also use any of the numerouspolymers including quaternized nitrogen atoms which are integral to thepolymer backbone, and other polymers having repeating quaternized units,as described by Borchardt in the '342 patent. Nitrogen-based cationicmoieties may be interspersed with and/or copolymerized with up to 65% byweight (preferably 1% to 65% by weight) nonionics such as acrylamide andeven some anionics such as acrylic acid or hydrolyzed acrylamide.Molecular weights of the polymers may be quite high —up to a million ormore. Such copolymers are included in my definition: of polycationicformation control additives useful in my invention.

Preferred anions for association with the quaternized nitrogen atoms arehalide anions, particularly chloride ions, which readily dissociate inthe aqueous drilling or other formation treatment fluid, but any anions,including formate anions, may be used which will not interfere with thepurposes of the formation treatment. Persons skilled in the art may wishto review the various anions mentioned in the above incorporatedpatents.

Thus it is seen that a cationic formation control additive useful in myinvention is a material having from one to hundreds or thousands ofcationic sites, generally either amines or quaternized amines, but mayinclude other cationic or quaternized sites such as phosphonium orsulfonium groups.

I employ potassium formate together with a cationic formation controladditive. The potassium formate may be added to the formation treatingor drilling fluid before or after the cationic formation controladditive, or may be made in situ by the reaction of potassium hydroxideand formic acid. The potassium hydroxide and formic acid may be added inany order, separately or together, before or after the addition of thecationic formation control additive, and need not be added in exactmolar proportions. Any effective amount of the combination of potassiumformate and formation control additive may be used, but I prefer to useratios of potassium formate to formation control additive of 25:75 to75:25 by weight in the solution, in combined concentrations of at least0.001% by weight in the drilling or other formation treatment fluid.Following are results from a clay pack flow test and a capillary suctiontest.

Clay Pack Flow Test Volume (higher the better) Elapsed time → 1 min- 3min- 5 10 CST Test products start ute utes min min time Fresh water 5 1517 23 25 225.2 2% KCl 15 87 175 102 1% KCl and 19 80 132 172 36.1 12 GPTKCOOH poly(DADMAC) 2 GPT 26 90 140 185 38.3 poly(DADMAC) + 21 83 132 170212 45.6 KCOOH 2 GPT poly(DADMAC) 1 GPT 22 52 72 86 112 63.8poly(DADMAC) + 21 74 112 140 179 40.9 KCOOH 1 GPT poly(DADMAC) + 5 21 2834 47 224.6 0.5 GPT poly(DADMAC) + 18 55 80 107 146 58.6 KCOOH 0.5 GPTLMWP (DADMAC) 14 42 64 82 107 68.4 2 GPT LMWP (DADMAC) 19 64 83 118 15657 2 GPT + KCOOH HMWP (DADMAC/AA) 8 26 38 48 60 165.8 2 GPT HMWP(DADMAC/ 17 48 71 88 114 60.6 AA) + KCOOH 2 GPT Monomer (DADMAC) 2 17 2230 42 239.6 2 GPT KCOOH (37%) 7 25 31 41 51 168.7 2 GPT Champion TMAC 136 63 75 109 146.4 2 GPT Champion TMAC 3 23 33 39 47 263.9 1 GPT TMAC 1GPT + 15 59 95 124 172 68.9 12 GPT KCOOH Poly(DADMAC) = 25%poly(diallyldimethyl ammonium chloride) TMAC = 25% by weight tetramethylammonium chloride GPT = gallons of the test additive(s) solution perthousand gallons of formation treatment (drilling) fluid HMWP = 15.5% byweight of the indicated high molecular weight polymer LMWP = 14.5% byweight of the indicated low molecular weight polymer KCOOH = 18% byweight aqueous solution

From the above table, it can be seen that the addition of potassiumformate to the formation control additives improved the resultsconsiderably. In the clay pack flow test, where the higher volumes at agiven time indicate better clay stability, the addition of a smallamount of potassium formate increased the volume throughput for a givenpolymer concentration. In fact, adding the potassium formate improvedthe performance of a polymer more than using twice the concentration ofthe polymer alone. For example, the poly(DADMAC) at 1 GPT treatment hada volume at 10 minutes of 112 ml. The same polymer, when combined withpotassium formate and treated at 0.5 GPT (half the original polymerconcentration), had a volume of 146 ml, indicating better clay stabilityand a possible synergistic effect from the addition of the potassiumformate.

Similar results are obtained from the CST data. In this test, a constantvolume of treated fluid is flowed across a clay and filter medium. Thelower the time for the volume to pass through, the better the claystabilization. The addition of potassium formate lowers the CST time innearly all cases, indicating a benefit in performance from the formate.The presence of potassium formate, as in the clay pack flow test, alsoindicates synergy with the polymer. The CST time for the poly(DADMAC)+potassium formate at 0.5 GPT is lower than the time for the higherconcentration (1 GPT) of polymer alone. Thus, the addition of potassiumformate is sufficiently beneficial to allow reducing the polymer byhalf, and still increase the performance.

In both the clay pack flow test and the CST, the polymer combinationswith the potassium formate were also better than the effect of formatealone. The CST result and the clay pack flow test volume for the 2 GPTof 37% potassium formate (by itself) were both worse than even the lowtreatment levels of the polymer/formate combinations, but better thansome of the polymer treatments alone. This indicates that, while thepotassium formate is effective alone and better than some polymer-onlytreatments, its performance is enhanced when combined with the formationcontrol additives.

What is claimed is:
 1. Method of reducing permeability damage in asubterranean formation from contact of a treatment fluid with saidsubterranean formation comprising contacting the subterranean formationwith an aqueous solution of said treatment fluid containing anitrogen-based cationic formation control additive and potassiumformate.
 2. Method of claim 1 wherein said potassium formate is presentin said aqueous solution in a ratio of 25:75 to 75:25 by weight to saidcationic formation control additive in a total concentration in saidtreatment fluid of at least 0.001% by weight.
 3. Method of claim 1wherein said cationic formation control additive is a polymer ofdimethyl diallyl ammonium chloride.
 4. Method of claim 1 wherein saidcationic formation control additive is a homopolymer of dimethyl diallylammonium chloride having a molecular weight from about 1000 to about500,000.
 5. Method of claim 1 wherein said potassium formate isgenerated in situ by the reaction of formic acid and potassium hydroxideor carbonate.
 6. Method of claim 1 wherein said formation controladditive is a single site amine or quaternary ammonium compound. 7.Method of claim 1 wherein said formation control additive is anoligocationic compound.
 8. Method of claim 1 wherein said formationcontrol additive is a cationic polymer.
 9. Method of claim 2 whereinsaid cationic formation control additive is tetramethyl ammoniumchloride.